Radiobiological characterization of laser driven particles

The long-term aim of developing laser based particle acceleration towards clinical application requires not only substantial technological progress, but also new technical solutions for dose delivery and quality assurance as well as comprehensive research on the radiobiological consequences of ultra-short radiation pulses with high pulse dose.
During the last years the laser driven technology was developed at such a rate that cell samples and small animals can be irradiated. Within the joint research project “onCOOPtics” extensive in vitro studies with several human tumor and normal tissue cells were already performed revealing comparable radiobiological effects of laser driven and conventional electron and proton beams1,2. Using the same cell lines, these results were substantiated comparing the radiobiological response to ultra-short pulsed electron bunches (pulse dose rates of ≤1012 Gy/min) and continuous electron delivery at the radiation source ELBE3.
In a second translational step, in vivo experiments were established. Although the experiments were motivated by future proton trials, first attempts were performed with electrons at the laser system JETI4, since the delivery of prescribed homogeneous doses to a 3D target volume is easier for electrons than for protons. A full scale animal experiment was realized for the HNSCC FaDu grown on nude mice ear. The radiation induced tumor growth delay was determined and compared to those obtained after similar treatment at a conventional clinical LINAC. Again, no significant difference in the radiation response to both radiation qualities was revealed, whereas the successful performance of such a comprehensive experiment campaign underlines the stability and reproducibility of all implemented methods and setup components5.
During this experiment campaign the changing tumour take rate and a high rate of secondary tumours were identified as limitations of the model that have to be improved before proton experiments and tumour control studies can be performed. In order to optimize the model Matrigel as medium for tumor cell injection and the glioblastoma cell line LN229 as interesting entity for proton treatment were introduced. Results of this optimization process and the status of the experiments with laser driven protons at the laser system DRACO will be presented.
The work was supported by the German Government, Federal Ministry of Education and Research, grant nos. 03ZIK445 and 03Z1N511.

1Laschinsky L, Baumann M, Beyreuther E, Enghardt W, Kaluza M et al. (2012) Radiobiological effectiveness of laser accelerated electrons in comparison to electron beams from a conventional linear accelerator. J. Radiat. Res. 53(3): 395-403.
2Zeil K, Baumann M, Beyreuther E, Burris-Mog T, Cowan TE et al. (2012) Dose-controlled irradiation of cancer cells with laser-accelerated proton pulses. Appl. Phys. B 110(4): 437-444.
3Beyreuther E, Karsch L, Laschinsky L, Leßmann E, Naumburger D et al. (2015) Radiobiological response to ultra-short pulsed megavoltage electron beams of ultra-high pulse dose rate. Int. J. Radiat. Biol. 91(8): 643-652.
4Brüchner K, Beyreuther E, Baumann M, Krause M, Oppelt M et al. (2014) Establishment of a small animal tumour model for in vivo studies with low energy laser accelerated particles. Radiat. Oncol. 9(1): 57.
5Oppelt M, Baumann M, Bergmann R, Beyreuther E, Brüchner K et al. (2015) Comparison study of in vivo dose response to laser-driven versus conventional electron beam. Radiat. Environ. Biophys. 54(2): 155-166.